Crashes in lmtpproxyd, and a patch

Giles Malet gdmalet at
Fri Nov 27 11:15:28 EST 2015

We have a bunch of servers in a murder, and I recently took a look in 
/var/lib/imap/cores and found core files for lmtpd/lmtpproxyd all over 
the place. These seem to be generated in waves, and can occur on the 
front end imap proxy servers, the incoming e-mail servers, and the 
mailbox servers -- often all at the same time, perhaps 10 cores in 20 
minutes ... then nothing for a month or two. The system keeps running 
well enough that we have not noticed problems.

I suspect this is load related, but am not sure. Perhaps something goes 
wrong on the mupdate server, and the wheel fall off downstream for a while?

Anyhow, I tracked it down to the following (patch: conn is null) in 
mupdate_client.c. We are running 2.4.17, but this patch is against the 
current HEAD of git:// . It stops the 
crash, but further than that I have no idea if this is a good thing, or 
if it just hides a bigger problem; I don't know the code well enough.

The call to the crashing mupdate_noop is coming from here, in lmtpd.c:

     /* get a connection to the mupdate server */
     r = 0;
     if (mhandle) {
     /* we have one already, test it */
     r = mupdate_noop(mhandle, mupdate_ignore_cb, NULL);
     if (r) {

I guess the test is failing when it crashes?

Hopefully this is useful - please reply if anyone needs more info.

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